1. Field of the Invention
This invention relates in general to deployable airfoil structures and particularly pertains to a self-deploying airfoil structure suitable for use on an artillery projectile or tube launched missile.
2. Prior Art
Improved ballistic performance and maneuverability is achieved through the use of airfoils on a projectile or missile and the like. However, in many devices employing aerodynamic forces for stability, lift or drag, it is necessary that airfoils such as wings, fins and the like be stowed within the body before deployment. The conventional method for doing so is to pivot an airfoil at one end and deploy it radially outward. This requires that a long axial slot must be cut in the skin of the projectile and the airfoil permitted to extend its full width into the body of the device. Such slots reduce the structural integrity of the skin and may seriously interfere with packaging of components. The present invention provides an airfoil which does not project into the skin its full width, thereby enhancing packaging efficiency and structural integrity. The present invention is instead designed to be self deployed from a stowed position in which the airfoil is folded down and forward with respect to the relative airstream and in a position which is substantially contiguous with the radial skin of the projectile.
The most relevant prior art known to the applicant is U.S. Pat. No. 4,664,339 to Crossfield issued May 12, 1987 and relating to a missle appendage deployment mechanism in which a radially contiguous stowed airfoil such as a wing or fin, when deployed rotates upwardly from a stowed into a feathered vertical position into the airstream of the missle or projectile. While this upward rotation from the stowed position is efficient from the standpoint of motion, it unfortunately requires that the attached end of the airfoil have a very complex shape in order to be compatible with a clevis with which is cooperates in order to achieve simultaneous rotation in two planes. The present invention overcomes the need for this complex prior art structure in the airfoil and cooperating elements by utilizing a novel combination of sequential motions the first of which is a tangential rotation in a plane tangential to the radial wall of the projectile and the second of which is a vertical rotation in a plane perpendicular to the axis of the projectile. While both the present invention and the Crossfield device exploit inherent aerodynamic forces to complete deployment of the airfoil, the unique sequential motion of the present invention permits the use of more conventional and thus less expensive structures both in the airfoil and in the attendant pivoting member or yoke thereby reducing the cost and complexity of the invention as compared to the prior art.
Other relevant prior art includes the following:
U.S. Pat. No. 4,323,208 to Ball is directed to a folding fin assembly for some type of flight vehicle which may be a guided/unguided missile. This disclosure relates to a two axis rotation and the fin is rotated about the axis Z--Z. The structure is mounted on a turntable which is rotatable with reference to the base about the axis W--W.
U.S. Pat. No. 3,098,445 to Jackson is directed to an aerodynamically supported rocket system. It uses a double rotation. When the blades are pivoted about the pivotal mounting of sleeves from the folded state of FIG. 1 to the radially extended state of FIG. 2, the cam arms engage the bottoms of the cam slots to rotate the blades to predetermined angular positions. Alternatively as the blades are pivoted to the folded state of FIG. 1, the cam arms engage the tops of the cam slots to rotate the blades to the fin position.
U.S. Pat. No. 4,667,899 to Wedertz is directed to a double swing wing self-erecting missible wing structure. This reference provides for a recess in the air frame in which the wing is stored in a retracted position. Each wing has a corresponding recess and there is a double rotation.
U.S. Pat. No. 3,063,375 to Hawley et al is directed to still another type of folding wing or folding fin. There is disclosed a rotation about an axis normal to the longitudinal axis of the missle and then a rotation about this axis to put it into the position shown in FIG. 6 for flight.